Power transformers are used to convert an AC power supply of the type available in homes, offices, hotels and the like, via an ordinary wall outlet, to a DC power supply compatible with electronic devices, such as radio telephones, telephones, answering machines, calculators, computers, radios, and the like. These power transformers are used to reduce dependence upon batteries, or to provide charging energy for rechargeable batteries from available AC power sources. To provide the regulated power supply, the transformer includes a power converting circuit within a housing having a male connector positioned thereon. The male connector is for connection to a female connector of a main power supply wall outlet.
Because power transformers are often used with portable devices, they have been developed to facilitate transport with the portable devices. One known transformer includes pivoting prongs that move into the transformer housing for storage during travel and pivot to an outwardly projecting position for connection to a wall outlet. These connectors have improved compactness when folded, to minimize the storage space that they require, thereby facilitating packing by travelers or commuters.
A difficulty encountered by travelers is powering their electronic equipment from the main power supplies found in different regions of the world. This difficulty arises because power supplies in different countries have different voltages, currents, and supply frequency characteristics. They also have different wall outlet female connector configurations. Although power converter circuits have been developed which produce a regulated DC voltage (e.g., five volts) from most main power supply signals found throughout the world, accommodating the different female connectors has been more difficult.
Typically, transformers have a male connector with prongs for one type of wall outlet. Adapters are employed to connect these connector prongs to other types of wall outlet female connectors. Such adapters have a female connector for receipt of the male connector prongs on the power transformer housing and a male connector for connection to the wall outlet female connector. A difficulty with these adapters is that they space the transformer housing from the wall outlet by at least the length of the prongs of the male connector on the power transformer housing. Because of this spacing, a substantial torque is exerted through the adapter to the wall outlet if a force is exerted against the transformer housing.
Accordingly, it is desirable to provide an improved universal power transformer system.